Cambridge - Azur 851E Preamp (Silver) Proprietary Terrapin amplification stages ; Audiophile grade oversize toroidal transformer ; Acousti Customisable front panel display ; Balanced and unbalanced analogue audio inputs for superior connec Flexible & configurable trigger outputs/IR and control bus for Custom Install integration and power THD (+ noise): &lt; 0.00045% @ 1kHz , &lt; 0.00057% @ 20kHz ; S/N (unweighted) : &lt; 110dBr , &lt; 90dBu Frequency response: 10Hz - 100kHz  0.1dB ; Output impedence:100 Ohms (Unbalanced or Balanced) ; Sub